1. Field of the Invention
The invention relates to machines for boring wells in rocks and more particularly to rock-breaking tools of self-propelled percussive-action machines for boring wells.
The present invention can advantageously be employed for boring wells in brittle rock of low toughness, for example, frozen soil of high toughness, coal and others.
The tool according to the invention can be used in mining, construction and wherever it is necessary to bore a deep well in tight quarters, for example, in mines where it is often difficult if not impossible to employ tubular rock-breaking tools, drills and augers with attendant bulky drilling equipment.
2. Description of the Prior Art
There is widely known a rock-breaking tool formed with a hollow cylinder having at one end an anvil block, and at the other end, the one oriented toward the bottom of a well being drilled, an annular cutting edge. Such a tool is termed a drill for making holes in various elements of building structures.
The principle of operation of the above rock-breaking tool consists in that the tool indents itself into an element of a building structure under the action of impacts from a head of a hand hammer or a hammer of a percussive-action machine, forming a core in its cylindrical cavity in the process. When the tool is withdrawn from the hole it drilled, the core is removed from the cylindrical cavity by striking against the cylinder.
However, such a rock-breaking tool is ineffective in boring wells 50 m and more-deep.
This is explained by that boring of deep wells requires a rock-breaking tool of a length equal to the depth of a well being bored.
The great length of the rock-breaking tool increases its weight proportionally. A considerable increase of the weight sharply decreases the impact transfer factor in the "tool-hammer" system at constant operational parameters of the percussive-action machine. A sharp drop in the impact transfer factor in the "tool-hammer" system makes the tool practically incapable of boring a well.
In addition, the great length of the rock-breaking tool adversely affects its service characteristics (transportation, assembly/disassembly, play in pipe connections impairing rigidity, deviations of bored wells and others).
There is also known another rock-breaking tool for percussive-action machines to bore wells in frozen soil (see, for example, the Author's Certificate of the USSR No. 293,312).
This rock-breaking tool is a cylindrical casing carrying on its top end an anvil block, and at the end facing the bottom of a well being drilled, an annular cutting edge, which is formed with intersecting conical surfaces. The casing is formed with a cylindrical chamber for receiving broken rock (core), the chamber communicating with an orifice in a lateral cylindrical wall of the casing for removing the core from the chamber into the space surrounding the casing. The height at which the orifice for removing the core from the casing is located in the wall of the casing is approximately equal to the specified depth of bored wells and ranges between 4 and 6 m. To direct the core from the cavity inside the casing into the orifice in the wall of the casing, the cylindrical part of the cavity contains a curvilinear partition which delimits the cavity in the top portion of the casing so forming a working cavity which faces the well bottom and accommodates the core. The curvilinear partition is intended for changing the direction of the core motion through 90.degree..
The above rock-breaking tool operates in the manner below.
When the anvil block of the rock-breaking tool receives impact pulses from the hammer of the impact-action machine, the tool indents itself by its annular cutting edge into rock to partly break it off in the zone of the edge. As the tool progressively indents itself into rock, the chamber in the casing gradually fills with the resultant core which advances toward the curvilinear partition and the orifice in the wall of the casing. Once the chamber of the casing is filled with the core, the rock-breaking tool is extracted and placed at a point of drilling the next well. As a new well is bored in the aforesaid manner, broken rock formed in the new well will displace the core from the first well due to translational motion of the rock-breaking tool. When a new well is bored to a previously specified depth, the core from the preceding well is completely displaced by the core from the second well.
Once boring is completed, the tool is tapped transversally, and the core slides out by gravity from the chamber.
All these rock-breaking tools are not suitable for practical use in boring of deep wells in low-tough rock and can be used only in conjunction with bulky equipment, such as diesel hammers. Additionally, they cannot be employed in self-propelled percussive-action machines because the core they cut does not pass through the narrow annulus between the casing of the self-propelled percussive-action machine and the well wall. Moreover, the core simply butts against the well wall when forced out of the casing chamber.